Process of reacting cellulose fibers with beta-propiolactone



United States Patent Ofiice 2,721,784 Patented Oct. 25, 1955 PROCESS OF REACTL FG CELLULOSE FIBERS WITH BETA-PROPHEPLACTONE NoDrawing. Application July 18, 1952, Serial No. 299,772

4 Claims. (Cl. 8115.6)

(Granted under Title 35, U. S. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, forall governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a process of chemically modifying cellulose fibers. More particularly the invention provides fibers composed essentially of cellulose betapropiolactone reaction products.

Although cellulose textile fibers have been chemically modified in numerous ways, only a few methods of chemically modifying them to produce textile fibers having greater effective diameters are known. Some cellulose textile fibers such as cotton fibers become swollen in solutions such as aqueous lyes, ethylamine or other aliphatic amines. However, when the surrounding liquid is removed and the fibers are dried, the swollen fibers generally collapse and have effective diameters substantially equal to those of the original diameters. Mercerizations, or treatments such as a partial carboxymethylation involving concurrent mercerizations, are known to permanently increase the effective diameters of cellulose textile fibers. However, the fibers so produced are characterized by a relatively great aflinity for water and other polar liquids.

The fibers produced by the present invention have markedly increased effective diameters, decreased afiinity for water and polar compounds, without a materially decreased tensile'strength. They have a dye resistance, heat resistance, acid induced degradation resistance, wrinkle resistance, and wool-like properties markedly greater than the fibers from which they are produced. They contain an appreciable proportion of olefinic unsaturated groups.

In general, according to the invention, cellulose fibers are reacted with beta-propiolactone at from about 50 to 155 C. until fibers are produced containing from about 0.5 to 26%, based on the weight of the original fibers, of beta-propiolactone reaction products combined with the cellulose, i. e. containing from about 0.5 to 26% beta-'propiolactone substituents. The increased weight is essentially due to the inclusionof beta-propiolactone reac tion products within the walls of the fibers. This is true whether the fibers are reacted with vapors of beta-propiolactone or with beta-propiolactone' in the liquid phase,

in the presence or absence of a solvent or a catalyst, or

- in the presence of an acidic or a basic catalyst.

Suitable cellulose fibers include cotton fibers and regenerated cellulose fibers such as viscose rayon fibers before or after bleaching, mercerization and the like treatments. Bleached, mercerized' cotton fibers are preferred. The cellulose fibers can be swollen in a swelling agent such as a lye solution and converted to swollen fibers immersed in a non-aqueous solvent by the conventional procedures of solvent exchange prior to reacting them withbeta-propiolactone. With most reactants the reaction of the swollen cellulose fibers isfaster and more the reactivity of the normal fibers in the process of this invention is sometimes equal to or in some cases greater than that of the swollen fibers.

The cellulose fibers can be reacted in the form of free fibers, sliver, yarn, or fabric. The use of yarns, threads or fabric is preferred.

The cellulose fibers are preferably reacted by immersing them in a boiling solution of beta-propiolactone. Suitable solvents for such solutions comprise organic liquids which are unreactive solvents for beta-propiolactone (i. e., are 'unreactive toward beta-propiolactone or cellulose and are capable of dissolving at least about 0.5 part of beta-propiolactone per part of solvent). (Throughout the specification and claims the term parts refers to parts by weight.) Examples of suitable solvents include hydrocarbons such as benzene, Xylene, and the normal, branch-chain, or cyclic hexanes, halohydrocarbons such as carbon tetrachloride, chloroform, tetrachloroethane, and chlorobenzene, and ketones such as acetone, methyl iso-butyl ketone, and methyl iso-propyl ketone, and ethers such as dioxane and the like organic solvents. The use of water immiscible unreactive solvents for beta-propiolactone having a relatively high boiling point, such as Xylene, tetrachloroethane, and the like, is preferred. The use of solutions of beta-propiolactone containing from about 5 to 20 parts of solvent per part of beta-propiolactone and the use of amounts of such solutions providing from about 1 to 4 parts of beta-propiolactone per part of cellulose is preferred.

Beta-propiolactone is known to etherify hydroxy compounds to form carboxyethyl ethers, to esterify hydroxy compounds to form 3-hydroxypropionic acid esters and also to polymerize. Presumably all of the three types of reactions occur in the beta-propiolactone reaction involved in the process of the present invention. While in general the etherification reaction is favored by acid catalysts or no catalysts and the esterification reaction is favored by basic catalysts with the polymerization reaction accompanying either of the above types of reaction, in the reaction involved in the process of the present invention, neither the acid or basic catalysts or the absence of a catalyst markedly influence the type of reaction which predominates.

In the reaction between cellulose and the vapors of beta-propiolactone the etherification reaction predominates. In reactions in which the beta-propiolactone is dissolved in a water immiscible solvent for beta-propiolactone (the preferred process of practicing the invention) the esterification reaction predominates.

The beta-propiolactone reacted fibers are preferably washed free of uncombined reactants with an organic solvent capable of dissolving polymers of beta-propiolactc-ne, for example, with solvents suchas acetone, alcohol, or dioxane. The washing substantially completely removes adhering uncombined beta-propiolactone polymeric products which are not deposited within the fiber walls and leaves the fibers with a soft, wool-like hand and feel.

The beta-propiolactone reacted fibers are useful for substantially any of the wide variety of uses known for cellulose fibers. They are particularly useful wherever wool-like properties and properties such as a dye resistance, a heat resistance, an acid induced degradation resistance and a wrinkle resistance markedly greater than those of cellulose textile fibers is important. In addition, the beta-propiolactone reacted fibers can readily be produced in the form of unsaturated compositions which undergo the reactions typical of organic compounds containing olefinic groups. These unsaturated fibers constitute valuable intermediates from which to prepare numerous different derivatives of cellulose in the form of textile fibers.

Beta-propiolactone reacted cellulose fibers are produced in the form of appreciably unsaturated fibers by dehydration at moderately elevated temperatures. A preferred process of producing them comprises immersing such fibers in a water immiscible inert organic liquid, refluxing the liquid, and isolating water from the liquid returning from the condenser. The water immiscible solvents for beta-propiolactone are preferred liquids for such employment. The dehydration is preferably conducted at from about 50 C. to about 150 C. The dehydration can be conducted by a wide variety of conventional procedures for dehydrating solid compositions at moderately elevated temperatures and can be conducted during the reaction of a cellulose textile fiber with beta-propiolactone so that the beta-propiolactone reacted cellulose textile fibers are subjected to dehydration as they are formed. Such unsaturated fibers are composed of materials of the group consisting of the components of cotton, the products of a cellulose-beta-propiolactone reaction and containing appreciable amounts of the dehydration products of cellulose-beta-propiolactone reaction products and beta-propiolactone polymers.

The following examples illustrate the invention in detail relative to the reaction of cellulose fibers with betapropiolactone dissolved in unreactive solvents.

EXAMPLE I Efiect of temperature and type of solvent Weighed skeins of mercerized 7/2 cotton thread were immersed for 4 hours in refluxing solutions consisting of 30 parts of the indicated solvent and 2 parts of betapropiolactone per part of cellulose. The beta-prpiolactone reacted textile fibers so produced were washed free of uncombined reactants and adhering polymers with acetone, then dried, weighed and analyzed.

The results of the analysis are recorded in Table I. The term percent carboxyethyl refers to the percent by weight of carboxyethyl as determined by addition of excess standard base and back titration with standard acid. The term percent BPL substituents refers to the percentage of the beta-propiolactone reaction products bound into modified cotton. The proportion of this increase in weight not accounted for by the percent carboxyethyl represents non-titratable combined beta-propiolactone reaction products.

1 It may be noted that the water miscible solvents, acetone and dioxane gave relatively low results compared to the results obtained with water immiscible solvents.

7 Corrected for 0.65% carboxyethyl content of the blank.

EXAMPLE II Efiect of time Skeins of unbleached 12/5 cotton sewing thread after de-waxing with acetone were immersed in refluxing solutions consisting of 20 parts of xylene and 2 parts of betapropiolactone per part of cellulose. The fibers produced were isolated and purified as described in Example I.

The results of an analysis of the fibers produced are recorded in Table H.

TABLE II Percent Percent Lbs.

Time of Reaction BP Oarboxy- Tensile Substitnents ethyl Strength It may be seen that when the fibers produced ar combined with more than about 26% beta-propiolactone reaction products their tensile strength decreases markedly.

EXAMPLE III Regenerated cellulose Three skeins of 1100/2 high tenacity viscose rayon tire cord were immersed for 5, 10, and 15 minutes respectively in refluxing solutions consisting of 20 parts of xylene and 2 parts of beta-propiolactone per part of ce1- lulose. The respective weight gains were 1.10, 1.83, and 3.24%. The respective carboxyethyl contents were 0.71, 1.62, and 2.39 percents.

EXAMPLE IV Catalysis Three skeins of 12/5 cotton thread were soaked in 2% solutions of monoammonium phosphate, diammonium phosphate and oxalic acid respectively, centrifuged to about 100% wet pickup, then dried in a blower oven at 60, and finally refluxed in 500 ml. of xylene containing 60 g. of beta-propiolactone for 15 minutes. The treated samples were extracted with acetone to remove non-reacted beta-propiolactone and polymer. Weight gains after extraction were 22.5%, 23.9% and 19.1%, respectively, and carboxyethyl contents of 11.7%, 12.5% and 9.7% respectively.

EXAMPLE V The experiment above was repeated using a 2% solution of sodium hydroxide as catalyst, refluxed in xylene and beta-propiolactone for 10 minutes.

The weight gain was 31.5% and carboxyethyl content 13.9%.

The following examples illustrate the invention in detail relative to the reaction of cellulose textile fibers with betapropiolactone vapors.

EXAMPLE VI Eflect of time A skein of dry 12/5 cotton thread was contacted at from to C. under 30 to 40 mm. pressure with the vapors from refluxing beta-propiolactone. No condensation was allowed to occur in the region containing the the thread.

In 20 minutes the weight of the thread had increased by about 1%. The carboxyethyl content of the thread produced was about 1%.

A skein of the same thread reacted in the same way for about 30 minutes increased in weight by 2.3%. The carboxyethyl content was 1.6%.

The following examples illustrate the invention in detail relative to employing the process of the invention to impart particular physical and chemical properties to cellulose textile fibers.

EXAMPLE VII Wrinkle proofing cloth Three samples of 80-square cotton print cloth were reacted for the indicated times.

The analytical results obtained on the products are recorded in Table III. The wrinkle recovery angles were determined on a Monsanto wrinkle recovery tester in the usual manner.

TABLE III BPL Sub- Carboxy- Wrinkle Time of Reaction stituents, ethyl, Recovery,

percent percent degrees EXAMPLE VIII Increasing the effective diameter of cellulose textile fibers substituents.

TABLE IV Itriihciregse in c ness Percent Beta-propiolaetonc substituents zfg over blank,

percent None (blank) 0. 0188 6.59 0. 0191 1. 6 26.90". 0. 0232 23. 4 46.92. 0. 0262 39. 4 56.10 0. 0283 50. 5

EXAMPLE IX Moisture regain The heretofore known methods of increasing the effective diameter of cotton textile fibers causes a concurrent increase in afiinity for water and polar liquids. This increased aflinity increases the tendency of the fibers to remain moist and to become readily soiled.

Samples of cotton thread reacted with beta-propiolactone until they contained the indicated amount of combined substituents were dried for two hours at 120 C. From the weight loss during the drying, the original moisture content of the thread was calculated. The samples were then allowed to come to equilibrium in a constant temperature-relative humidity atmosphere (70 F. and 65% relative humidity) and reweighed. From their increase in weight, their moisture regain was calculated. The values obtained from the reacted samples and from an untreated control sample are recorded in Table V.

TABLE V original Moisture BPL substituents, percent g fig f Regain,

Y percent percent EXAMPLE X Resistance to heat induced degradation Samples of mercerized 7/ 2 cotton sewing thread before and after reaction with beta-propiolactone to the indicated extent were heated for days at 125 C. in an electric oven.

The amount of the original tensile strength which was retained by the samplesand. an untreated control sample is. recorded in Table. VI.

TABLE VI BPL Substz, percent 551 1151 Ester Ester/Ether t a t i ri percent percent Ratio percent '0 0 35.8 0. 49 0' a 46. 3 1. 49 0. 35' 0:23 54. 2 2. 34 2. 58 1. 10 62. 1 2. 20 5. O2 2. 28 66. 3 1. 6. 58 3.55 T 67. 5 5. 40 20. 20 3.74 r I 74. 4 9. 92 15. 73 11 59 '55. 1

1 Corrected for 0.30% for untreated control. 1 This sample had identical BPL take-up but higher carboxyethyl content, lower ester/ether rationote drop in strength retention.

It is apparent that the resistance to heat-induced degradation increases as the ester content of the combined betapropiolactone reaction products increases.

The strength retained by samples of mercerized 7 2 cotton sewing thread after beta-propiolactone reaction to the indicated extent followed by neutralizing the carboxyethyl groups with ammonia is recorded in Table VII.

TABLE VII Percent B PL Ma e Substituents Mercerized cotton Mercerized cotton control BPIJStreated cotton.

1 Control was soaked in dilute NH4OH (same as BPL-treated samples) washed in distilled Water and dried.

EXAMPLE XI Resistance to acid induced degradation Plain and mercerized 12/5 cotton sewing thread treated with beta-propiolactone were placed in a desiccator with untreated controls. The desiccator was evacuated and the air replaced with nitrous oxide gas and allowed to stand for six hours. The samples were then washed with water, dried and tested for tensile strength. Results are shown in Table VIII.

EXAMPLE XII Unsaturated textile fibers Samples of beta-propiolactone reacted cotton 7/2 thread were refluxed in xylene for three hours. A Stark and Dean trap was connected to the condenser and water formed in the reaction was removed azeotropically.

Table IX indicates the bromine absorption values before and after treatment. The values indicate that double bonds were formed by the dehydration treatment.

TABLE IX Bromine Bromine Absorption Absorption gig gfifi Before After Absorption Heating, Heating Percent Percent Percent Percent BPL substituents beta-propiolactone at about from 50 to 155 C. until fibers are produced containing from about 0.5 to 26%, based on the weight of the original fibers, of beta-propiolactone reaction products combined with the cellulose.

5 2. The process of claim 1 wherein the reaction is conducted by immersing the fibers in the beta-propiolactone dissolved in an inert solvent.

3. The process of claim 2 wherein the reaction is conducted by boiling the solution of the beta-propiolactone at 10 normal pressure.

4. The process of claim 3 wherein the solvent is xylene.

No references cited. 

1. A PROCESS COMPRISING REACTING CELLULOSE FIBERS WITH BETA-PROPIOLACTONE AT ABOUT FROM 50* TO 155* C. UNTIL FIBERS AND PRODUCED CONTAINING FROM ABOUT 0.5 TO 26%, BASED ON THE WEIGHT OF THE ORIGINAL FIBERS, OF BETA-PROPIOLACTONE REACTION PRODUCTS COMBINED WITH THE CELLULOSE. 